From 0d0ca8572f3847f38af8dec4ad4328ec7a170ec9 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Thu, 12 Jun 2008 20:55:39 +0000
Subject: [PATCH] Revert 52223.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52243 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/TailDuplication.cpp      | 18 ------------------
 .../TailDup/2008-06-11-AvoidDupLoopHeader.ll   |  4 ++--
 2 files changed, 2 insertions(+), 20 deletions(-)

diff --git a/lib/Transforms/Scalar/TailDuplication.cpp b/lib/Transforms/Scalar/TailDuplication.cpp
index 4e0949a2b47..d0998ab5a65 100644
--- a/lib/Transforms/Scalar/TailDuplication.cpp
+++ b/lib/Transforms/Scalar/TailDuplication.cpp
@@ -33,7 +33,6 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/Analysis/LoopInfo.h"
 #include <map>
 using namespace llvm;
 
@@ -51,12 +50,10 @@ namespace {
     static char ID; // Pass identification, replacement for typeid
     TailDup() : FunctionPass((intptr_t)&ID) {}
 
-    virtual void getAnalysisUsage(AnalysisUsage &AU) const;
   private:
     inline bool shouldEliminateUnconditionalBranch(TerminatorInst *, unsigned);
     inline void eliminateUnconditionalBranch(BranchInst *BI);
     SmallPtrSet<BasicBlock*, 4> CycleDetector;
-    LoopInfo *LI;  // The current loop information
   };
 }
 
@@ -72,9 +69,6 @@ FunctionPass *llvm::createTailDuplicationPass() { return new TailDup(); }
 /// a place it already pointed to earlier; see PR 2323.
 bool TailDup::runOnFunction(Function &F) {
   bool Changed = false;
-
-  LI = &getAnalysis<LoopInfo>();
-
   CycleDetector.clear();
   for (Function::iterator I = F.begin(), E = F.end(); I != E; ) {
     if (shouldEliminateUnconditionalBranch(I->getTerminator(),
@@ -89,10 +83,6 @@ bool TailDup::runOnFunction(Function &F) {
   return Changed;
 }
 
-void TailDup::getAnalysisUsage(AnalysisUsage &AU) const {
-  AU.addRequired<LoopInfo>();
-}
-
 /// shouldEliminateUnconditionalBranch - Return true if this branch looks
 /// attractive to eliminate.  We eliminate the branch if the destination basic
 /// block has <= 5 instructions in it, not counting PHI nodes.  In practice,
@@ -196,14 +186,6 @@ bool TailDup::shouldEliminateUnconditionalBranch(TerminatorInst *TI,
   if (!CycleDetector.insert(Dest))
     return false;
 
-  // Avoid non-natural loops:
-  // If a loop header is duplicated, the former natural loop will contain two
-  // paths into the loop --> the loop it not natural anymore. We want to avoid
-  // this, because other optimizaions may fail to improve the loop because of 
-  // this.
-  if (LI->isLoopHeader(Dest))
-    return false;
-
   return true;
 }
 
diff --git a/test/Transforms/TailDup/2008-06-11-AvoidDupLoopHeader.ll b/test/Transforms/TailDup/2008-06-11-AvoidDupLoopHeader.ll
index 7014f744a80..c29e7d45c6a 100644
--- a/test/Transforms/TailDup/2008-06-11-AvoidDupLoopHeader.ll
+++ b/test/Transforms/TailDup/2008-06-11-AvoidDupLoopHeader.ll
@@ -1,5 +1,5 @@
-; RUN: llvm-as < %s | opt -tailduplicate -taildup-threshold=3 -stats -disable-output |& \
-; RUN:   not grep tailduplicate
+; RUN: llvm-as < %s | opt -tailduplicate -taildup-threshold=3 -stats -disable-output | not grep tailduplicate
+; XFAIL: *
 
 define i32 @foo(i32 %l) nounwind  {
 entry: